The present invention relates to high-performance radiation sensitive resist compositions and their use in lithography processes to fabricate semiconductor devices. Specifically, the present invention is concerned with negative-tone silicon-containing resist compositions based on an acid catalyzed crosslinking of certain silicon-containing polymers. The resist composition of the present invention can be used to fabricate semiconductor devices using various irradiation sources, such as mid-ultraviolet (UV), deep-UV (for example 248 nm, 193 nm and 157 nm), extreme UV, X-ray, electron-beam and ion-beam irradiation. The resist compositions of the present invention exhibit enhanced sensitivity to e-beam and i-line irradiation along with resistance to high etch resistance to reactive ion etching in the presence of oxygen and chlorine. Compositions of the present invention are developable in aqueous base compositions.
In the manufacture of patterned devices such as semiconductor chips and chip carriers the steps of etching different layers, which constitute the finished product are among the most critical and crucial steps involved.
In semiconductor manufacturing, optical lithography has been the main stream approach to pattern semiconductor devices. In typical prior art lithography processes, UV light is projected onto a silicon wafer coated with a layer of photosensitive resist through a mask that defines a particular circuitry pattern. Exposure to UV light, followed by subsequent baking, induces a photochemical reaction, which changes the solubility of the exposed regions of the photosensitive resist. Thereafter, an appropriate developer, typically an aqueous base solution, is used to selectively remove the resist either in the exposed regions (positive-tone resists) or, in the unexposed region (negative-tone resists). The pattern thus defined is then imprinted on the silicon wafer by etching away the regions that are not protected by the resist with a dry or wet etch process.
The current state-of-the-art optical lithography uses DUV irradiation at a wavelength of 248 nm to print features as small as 250 nm in volume semiconductor manufacturing. The continued drive for the miniaturization of semiconductor devices places increasingly stringent requirements for resist materials, including high resolution, wide process latitude, good profile control and excellent plasma etch resistance for image transfer to substrate. Several techniques for enhancing the resolution, such as reduced irradiation wavelength (from 248 nm to 193 nm), higher numerical aperture (NA) of the exposure systems, use of alternate masks or illumination conditions, and reduced resist film thickness are currently being pursued. However, each of these approaches to enhance resolution suffers from various tradeoffs in process latitude, subsequent substrate etching and cost. For example, increasing NA of the exposure tools also leads to a dramatic reduction in the depth of focus. The reduction in the resist film thickness results in the concomitant detrimental effect of decreased etch resistance of the resist film for substrate etching. This detrimental effect is exasperated by the phenomenon of etch induced micro-channel formation during substrate etch, effectively rendering the top 0.2-0.3 um resist film useless as an etch mask for substrate etching.
Achieving further miniaturization would be facilitated by providing resists that exhibit enhanced sensitivity to e-beam and e-beam irradiation. However, obtaining resists that are sensitive to e-beam and i-line as well as being highly resistant to plasma and reactive ion etching is not an easy task. This is further complicated if a water developable system instead of an organic solvent developable system is desired.
Most lithographic processes (excluding so-called direct-write techniques) typically employ some type of patterned mask through which the imaging radiation is projected onto the resist material to be patterned on the substrate of interest. Typically, the mask itself is formed by a lithographic technique such as direct-write electron beam lithography or in some instances by projection UV lithography (especially i-line or deep UV) using an appropriate resist material. Typically, the mask comprises a patterned metal layer(s) (e.g., chromium) on a quartz plate (or other transparent plate).
A resist composition must possess desirable radiation response characteristics to enable image resolution upon exposure to a desired radiation development. Thus, a patternwise exposed positive resist must be capable of appropriate response (i.e. selective dissolution of exposed areas) to a developer to yield the desired resist structure. Given the extensive experience in the lithographic arts with the use of aqueous alkaline developers, it is important to achieve appropriate dissolution behavior in such commonly used developer solutions.
The resist composition must also possess suitable chemical and mechanical properties to enable transfer to the image from the patterned resist to an underlying substrate layer(s). Typically, pattern transfer is performed by some form of wet chemical etching or ion etching. The ability of the patterned resist layer to withstand the pattern transfer etch process (i.e., the etch resistance of the resist layer) is an important characteristic of the resist composition. In the case of typical mask making processes, a chlorine-containing etchant such as combination of Cl2 and O2 is generally a preferred etchant. Halogen-based etchants other than fluorine (i.e., Cl, Br, or I) are also preferred etchants for patterning metals and semiconductor (e.g., polycrystalline silicon) materials.
With demands for finer detailed masks and patterned metals/semiconductor materials, the performance of higher atomic weight halogen-based (i.e., Cl, Br, or I) etching processes has been increasingly problematic due to excessive erosion of the resist during the etching step needed for pattern transfer. Additionally, the desire to use lower energy e-beam imaging tools (e.g., 10 KeV tools) generally means that the resist layer must be thinner to be imaged by the lower energy beam. Thus, there is a need for improved processes for making patterned metal and/or semiconductor features and especially for making lithographic masks containing patterned metal layers.
It would therefore be desirable to provide a resist composition that has all of the above-mentioned attributes.
Accordingly, to the present invention a highly sensitive, high resolution negative-tone resist compositions is provided.
In addition, resist compositions of the present invention exhibit high resistance to reactive ion etching in employing oxygen and/or chlorine. Furthermore, resist compositions of the present invention can be developed in aqueous base compositions.
More particularly, the negative-tone resist compositions of the present invention comprise:
(a) a silicon-containing polymer with pendant fused moieties selected from the group consisting of fused aliphatic moieties, homocyclic fused aromatic moieties, and heterocyclic fused aromatic moieties and sites for reaction with a crosslinking agent,
(b) an acid-sensitive crosslinking agent, and
(c) a radiation-sensitive acid generator.
Another aspect of the present invention relates to a method of forming a patterned material layer on a substrate. The method comprises:
(a) providing a substrate having a material layer on a surface,
(b) providing a layer of resist over the material layer, the resist comprising:
(i) a silicon-containing polymer with pendant fused moieties selected from the group consisting of fused aliphatic moieties, homocyclic fused aromatic moieties, and heterocyclic fused aromatic moieties and sites for reaction with a crosslinking agent,
(ii) an acid-sensitive crosslinking agent, and
(iii) a radiation-sensitive acid generator;
(c) patternwise exposing the resist layer to imaging radiation,
(d) removing portions of the resist layer not exposed in step (c) to create spaces in the resist layer corresponding to the pattern, and
(e) removing portions of the material layer at the spaces.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.